The present invention relates generally to oil condition sensors.
In order to protect an engine from damage, it is necessary to change the lubricating oil when it deteriorates. On board oil conditions sensors have been provided that measure oil condition parameters, e.g., conductivity, in order to determine if the oil can still provide the proper lubrication for the engine. Other parameters can be determined by taking a sample of the engine oil and testing it at a laboratory.
One such parameter is the quantity of wear metals in the engine oil. The wear metals are debris worn off internal engine parts caused by part-to-part contact. The most common of the wear metals is iron that is worn off of the pistons, cylinder walls, rings, valves, valve guides, gears, and bearings. The wear metals become oil-borne and the quantity of wear metals within the engine oil provide an indication of the condition of the oil. Specifically, as the quantity of wear metals in the oil increase, the condition of the oil worsens.
Typically, to determine the volume of wear metals in the engine oil, a sample is taken to a laboratory and the solids are separated from the oil. Then, the solids are burned in a plasma and the light from the burning solids is directed into a spectrometer. The wavelength and intensity of the light provides an indication as to the type and quantity of metal present in the oil sample. This method is an effective way to determine the wear metals present in the lubricating oil. However, it cannot be performed on board the vehicle. Moreover, it is expensive and the engine typically is taken out of service while the test is being performed.
The present invention has recognized these prior art drawbacks, and has provided the below-disclosed solutions to one or more of the prior art deficiencies.
A ferromagnetic particle sensor includes a hollow housing. A first electromagnet and a second electromagnet are supported by the housing. Moreover, a mass sensitive surface acoustic wave sensor is disposed vertically between the electromagnets.
In a preferred embodiment, the housing includes a base and the sensor further includes a circuit board extending from the base of the housing between the electromagnets. The mass sensitive acoustic wave sensor is attached to the circuit board. Preferably, the first electromagnet includes a coil wound around a core and the second electromagnet includes a coil wound around a core and the cores are made from a soft magnetic material.
In a preferred embodiment, the base is formed with external threads and the sensor is installed in a fluid reservoir that has a bore formed with correspondingly sized and shaped internal threads. Moreover, the reservoir defines an exterior surface and the base includes a flange that abuts the exterior surface of the reservoir when the sensor is installed therein. Also, in a preferred embodiment, the base includes an xe2x80x9cOxe2x80x9d ring groove that circumscribes the base and the sensor further comprises an xe2x80x9cOxe2x80x9d ring disposed therein. Preferably, the continuous sidewall is formed with one or more holes to allow oil to flow therethrough.
In another aspect of the present invention, a method for measuring ferromagnetic particles in lubricating fluid includes providing a first electromagnet and a second electromagnet. A mass sensitive surface acoustic wave sensor is disposed between the electromagnets. The electromagnets are selectively energized to attract ferromagnetic particles toward the mass sensitive surface acoustic wave sensor.
In yet another aspect of the present invention, a ferromagnetic particle sensor includes a hollow housing that defines an interior. Moreover, the sensor includes means for drawing ferromagnetic particles into the interior of the housing and means for sensing the mass of any ferromagnetic particles within the interior of the housing.
In another aspect of the present invention, a method for measuring ferromagnetic particles in lubricating fluid that has moving parts disposed therein includes providing a first electromagnet and a second electromagnet. A mass sensitive surface acoustic wave sensor is disposed between the electromagnets. The mass sensitive surface acoustic wave sensor includes a reference radio frequency amplifier that outputs a reference frequency and a sample radio frequency amplifier that outputs a sample frequency. In this aspect a difference frequency is determined based on the reference frequency and the sample frequency. Moreover, a wear rate of the parts disposed in the lubricating fluid is determined based on the difference frequency.
The present invention will now be described, by way of example, with reference to the accompanying drawings, in which: